JPH0954150A - Diversity receiving-type gps receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a diversity receiving-type GPS receiver of high positioning accuracy which can receive GPS waves well even in an area where it is hard to receive the waves, e.g. in cities, mountains, etc., thereby enabling positioning. SOLUTION: Receiving antennas 1a, 1b, RF receiving parts 2a, 2b and operation parts 3a, 3b are prepared. The operation part 3a, 3b operates a PDOP at a satellite from which the receiving antenna 1a, 1b can receive waves (a decrease rate of a positioning accuracy at the satellite), and also operates the present position. A switching/controlling part 5 selects the best among the PDOPs and switches a switching part 4. The resulting present position is displayed at a display part 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention receives a radio wave transmitted from a plurality of artificial satellites, and calculates a current position based on the received signals by a GPS (Global Positioning System).
tem) receiver, and more particularly to a diversity receiver type GPS receiver having a plurality of receiving antennas.

[0002]

2. Description of the Related Art In recent years, a GPS positioning system has been attracting attention as a navigation system for moving bodies such as vehicles and ships. The GPS system receives radio waves from three or more satellites in the two-dimensional side and four or more satellites in the three-dimensional side among radio waves from twenty or more artificial satellites orbiting the earth. Then, based on the received data, the distance between each satellite and the mobile body equipped with the system is calculated, and the current position of the mobile body, that is, the user is calculated from the calculated distance.

In the GPS system, it is necessary to receive radio waves from satellites, but in places with poor visibility of the sky, such as urban areas and mountains, the radio waves from satellites are blocked.
There is a problem that the required number of satellites (3 to 4) cannot be received, the positioning accuracy deteriorates, or the positioning becomes impossible in the worst case.

As a technique for compensating for this problem, conventionally, a diversity receiver as shown in FIG. 5 has been proposed. In FIG. 5, la and lb are receiving antennas, 2 is an RF receiving unit that demodulates the received RF signal and outputs demodulated data, 3 is a computing unit that computes its own current position based on the demodulated data, and 4 is a receiving antenna A switching unit for selectively switching the reception signals from la and lb, 5 is a switching control unit for performing antenna switching control based on the reception signal level obtained by the RF reception unit 2, and 6 is obtained by the calculation unit 3. The display unit displays the current position, for example, on the map.

In this configuration, two receiving antennas 1
The a and 1b are installed so that the reception signal levels of both antennas are uncorrelated, for example, they are arranged at the front part and the rear part of the vehicle. In the RF receiver 2, the antenna la or l
The received signal received in b is demodulated and sent to the arithmetic unit 3, and the received signal level is detected, and the switching control unit 5
To send to. In the switching control unit 5, the two antennas la and l are based on the received signal level sent from the RF receiving unit 2.
The switching unit 4 is controlled so that the antenna with the higher received signal level is selected from b. In the calculation unit 3, the RF reception unit 2
Calculate the current position of the self based on the demodulated data obtained in
The current position of the self is displayed on the display unit 6 on a map or the like.

[0006]

However, the GPS
The cause of the positioning error in the receiver is related not only to the received signal level, but also to the arrangement of the satellites receiving it. For this reason, when selecting only the received signal level, if both antennas have a received signal level above a certain level, only satellites that are arranged so that the positioning error will become large if the received signal level is switched when switching is performed. There is a drawback in that a good antenna is not switched in order to improve positioning accuracy by selecting a non-existent antenna.

The present invention was devised to solve the above problems, and an object thereof is to provide a diversity receiving GPS receiver for switching antennas capable of receiving satellites so as to minimize positioning error. To provide.

[0008]

A diversity receiving GPS receiver according to claim 1 of the present invention selects a plurality of receiving antennas for receiving signals transmitted from a plurality of satellites and a receiving signal at these receiving antennas. Switching unit for dynamically switching, an RF receiving unit for demodulating the reception signal selected by the switching unit, and a current position of the self based on the multi-tone signal data of the RF receiving unit, and a positioning accuracy deterioration rate. A calculation unit that calculates (DOP: Dilution of Precision) and a switching control unit that controls the switching unit so that the positioning accuracy deterioration rate for each receiving antenna calculated by the calculation unit becomes smaller. It is characterized by that.

In GPS, the positioning accuracy changes greatly depending on the arrangement of satellites. It is the DOP (positioning accuracy reduction rate) that determines whether the satellite constellation is good or bad, and the positioning error is DO.
It increases in proportion to the value of P. That is, positioning accuracy can be improved if an antenna receiving a combination of satellites having a small DOP value can be selected. According to the configuration of claim 1, the signals transmitted from the plurality of satellites are received by the plurality of receiving antennas. Received signals from these receiving antennas are selectively connected in the switching unit. The received signal is guided to the RF receiver and demodulated in the RF receiver. This demodulated signal includes satellite orbit data, data transmission time, and the like. Next, this demodulated data is input to the calculation unit. The calculation unit calculates the current position based on the demodulated data, calculates the positioning accuracy deterioration rate (DOP) of the currently selected satellite group, and sends this to the control unit. The control unit compares the value of this positioning accuracy deterioration rate (DOP) with a predetermined threshold value, and when it is larger than the threshold value, controls the switching unit to switch the receiving antenna, and when it is smaller than the threshold value. Continue to use the currently selected receiving antenna. The current position information obtained in this way is guided to the display unit and displayed in a form that is easy for the user to understand (for example, on a map). Even if there is only one reception system including the RF reception unit and the calculation unit, good reception can be performed in an area where the reception situation is poor.

A diversity receiving GPS receiver according to a second aspect of the present invention includes a plurality of receiving antennas for receiving signals transmitted from a plurality of satellites, and a plurality of receiving antennas respectively connected to the receiving antennas for demodulating the received signals. RF receivers, a plurality of calculators that are respectively connected to the RF receivers, calculate the current position of the self based on the demodulated signal data, and calculate a positioning accuracy deterioration rate (DOP); A switching unit for selectively switching the calculation result of the calculation unit,
A display unit that displays the current position based on the calculation result of the calculation unit selected by the switching unit, and the switching unit that reduces the positioning accuracy deterioration rate for each receiving antenna calculated by each calculation unit. And a switching control unit for controlling the unit. A signal transmitted from a plurality of satellites is received at each of a plurality of antennas. The received signal is demodulated by the RF receiving section provided for each receiving antenna, and the positioning of the current position and the calculation of the positioning accuracy degradation rate (DOP) are performed by each computing section. All the positioning accuracy deterioration rate data obtained for each receiving antenna is sent to the switching control unit. The switching control unit controls the switching unit to select the smallest one of the input positioning accuracy deterioration rates and to select the receiving system. As a result, the current position, which is the only selected calculation result, is guided to the display unit and displayed in a form that is easy for the user to see.

In short, among the receiving states of the receiving antennas that change momentarily depending on the surrounding conditions, the receiving antenna that can receive the satellite group that gives the best characteristics is selected, and the receiving state of the radio waves from the satellites is poor. Good positioning can be performed even in a place.

According to a third aspect of the present invention, there is provided a diversity receiving GPS receiver according to the first or second aspect, wherein the switching control unit switches the switching unit when the positioning accuracy deterioration rate is larger than a predetermined threshold value. It is characterized in that the switching section is switched by referring to the received signal level from the RF receiving section when the switching accuracy reduction rate is smaller than a predetermined threshold value. Positioning accuracy degradation rate (DO
When P) is larger than a predetermined threshold value, the receiving antenna is switched.
Refer to the received signal level from the receiving unit, select the antenna with the higher level if the receiving system is 2 systems, and select the antenna with the higher level when the receiving system is 1 system, and if the level is greater than the level threshold The antenna is maintained, and the antenna is switched when it is smaller than the threshold value. Since not only the positioning accuracy deterioration rate is used for determination but also the received signal level is also viewed, finer control can be performed.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a diversity receiving GPS receiver according to the present invention will be described below with reference to the drawings.

[First Embodiment] FIG. 1 is a block diagram showing an electrical configuration of a diversity receiving GPS receiver according to a first embodiment. The first embodiment relates to claim 2. For convenience, the claim 2 will be described first.

In the figure, la and 1b are GPS satellites (GPS:
The receiving antennas 2a and 2b for receiving radio waves from the Global Positioning System) are receiving antennas 1a,
RF receivers 3a, 3b that individually demodulate the received signals from 1b and output received data such as satellite orbit information and time information
Calculates its own current position based on the information of the received data from each RF receiver 2a, 2b, and reduces the positioning accuracy degradation rate (PDOP: Position Dilution of Pre) depending on the satellite position.
The calculation unit 4 for calculating the cision), the switching unit 5 for selectively switching the connection state between the calculation units 3a and 3b and the display unit 6, and the reference numeral 5 the positioning accuracy reduction rate (P) from the calculation units 3a and 3b.
DOP) value is compared to perform switching control of the switching unit 4, and 6 is a position on the map based on the positioning result selected by the switching unit 4, and a latitude / longitude display by text or the like on the map. Is a display unit that is displayed on the screen in a form that is easy for users to understand.

Here, the receiving antennas 1a and 1b are installed separately from, for example, the dashboard and the rear tray of the vehicle so that the two antennas have no correlation and the receiving states are different. The received signals received are sent to the RF receivers 2a and 2b, respectively.

The RF receivers 2a and 2b are multi-channel RF receivers capable of simultaneously demodulating radio waves from four or more satellites, and can simultaneously demodulate radio waves from, for example, five satellites. This is a 5-channel RF receiver. Four of the five channels demodulate the radio waves of the satellites used to calculate the current position, and the remaining l channel tracks the other satellites.

The received data demodulated in this way is sent to the arithmetic units 3a and 3b. The computing units 3a and 3b first calculate PDOP (positioning accuracy degradation rate due to satellite position) based on the demodulated data.

Calculation of PDOP is performed as follows. Matrix A,

[0020]

[Equation 1]

[0021] Where α, β and γ are

[0022]

[Equation 2]

It is However, (x _i , y _i , z _i ) represents the position of the i-th satellite, and (x ′, y ′, z ′) represents the coordinates of the positioning point (current position: unknown) (x ₀ , y ₀ , z ₀ )
It is the corrected coordinates when. Also, r _i ′ is the corrected distance from each satellite to the positioning point. When A ⁻¹ is an inverse matrix of the matrix A and A ^T is a transposed matrix in which the rows and columns of the matrix A are interchanged, a weighting coefficient matrix (A ^T · A) ⁻¹ is given,

[0024]

(Equation 3)

[0025] Then, the positioning accuracy degradation rate PDOP (P represents the position in Position) according to the satellite position is

[0026]

(Equation 4)

## EQU1 ##

In place of PDOP, GDOP (geometrical positioning accuracy reduction rate) and TDO given as follows are given.
You may use P (positioning accuracy fall rate with time).

[0029]

(Equation 5)

[0030]

(Equation 6)

Here, a ₄₄ represents a time element. PDO
Which of P, GDOP and TDOP is adopted is arbitrary and there is no special difference. PDOP is sufficient for measuring the three-dimensional position of a moving body such as a vehicle.

Now, the PDOP (positioning accuracy deterioration rate depending on the satellite position) is calculated for a combination of four satellites having the highest PDOP in the satellite group when five or more satellites are captured. And the calculation. When the number of satellites that can be captured is 3 or 4, the PDOP in this combination is used. If the number of satellites that can be captured is less than 3, PDOP cannot be calculated, so the maximum value is set. The value of PDOP calculated in this way is sent to the switching control unit 5. Then, when three or more satellites have been captured, the present position of the self is calculated using the received data in the combination of satellites when the previous PDOP was calculated. The data of this current position is sent to the switching unit 4.

The switching control section 5 compares the PDOPs calculated by the calculation sections 3a and 3b. Here, if the value of PDOP obtained by the first calculation unit 3a is smaller, the switching unit 4
To the side that receives the data of the first arithmetic unit 3a, and if the value of PDOP obtained by the second arithmetic unit 3b is smaller, the switching unit 4 is switched to the side that receives the data of the second arithmetic unit 3b. . If both values are the same, switching is not performed. The data of the current position selected by the switching unit 4 in this manner is sent to the display unit 6.

The display unit 8 displays on the screen a map showing its current position on the map. By doing so, it is possible to perform good GPS positioning even in urban areas and mountainous areas where reception is poor.

[Second Embodiment] FIG. 2 is a block diagram showing an electrical configuration of a diversity receiving GPS receiver according to a second embodiment. The second embodiment relates to claim 1. In the figure, the components having the same reference numerals as those in FIG. 1 have the same functions. 2 is an RF receiver, 3
Is an operation unit. The receiving antennas 1a and 1b are provided such that the two antennas are uncorrelated as in the case of the first embodiment. Now, for example, it is assumed that the switching unit 4 is connected to the receiving antenna la. Then, the receiving antenna 1
The reception signal received in a is transmitted to the RF receiver 2.
The RF receiver 2 demodulates the received signal and sends the received data to the calculator 3. The operation unit 3 calculates PDOP (positioning accuracy deterioration rate depending on the satellite position) from the received data. This is also the same as in the case of the first embodiment, when the number of satellites that can be received is less than 3, the maximum value is obtained, and when the number of satellites that can be received is 3 to 4, the maximum value of that satellite is also obtained. When the number of combined PDOPs is 5 or more, the optimum PDOP for the combination of four satellites is calculated from the values, and the calculated PDOP is sent to the switching control unit 5. In addition, the present position of the self is calculated based on the data of the satellite group at this time and output to the display unit 6 and displayed on the screen. The switching control unit 5 includes
A predetermined threshold value is set in advance. When the value of PDOP obtained by the arithmetic unit 3 is larger than this threshold value, the switching unit 4 is controlled to switch from the state of selecting the receiving antenna 1a to the state of selecting the receiving antenna 1b.

On the contrary, when the value is less than the threshold value, the receiving antenna 1a currently used is continuously used. By doing so, even if there is only one reception system including the RF reception unit and the calculation unit, good reception can be performed in an area where the reception situation is poor.

[Third Embodiment] FIG. 3 is a block diagram showing an electrical configuration of a diversity receiving GPS receiver according to a third embodiment. In the figure, the same reference numerals as those in FIG. 1 indicate that they have the same or equivalent functions. Here, the receiving antennas 1a and 1b are provided so as to be uncorrelated with each other, as in the above-described first and second embodiments. Then, the received signals are demodulated by the RF reception units 2a and 2b, respectively, and the calculation units 3a and 3b calculate PDOP (positioning accuracy deterioration rate depending on the satellite position) and calculate the current position of the self.

In the third embodiment, the switching control section 5 includes the RF receiving section 2a, the PDOP from the computing sections 3a and 3b, and the RF receiving section 2a.
The received signal level at 2b is also input. The reception signal level is output for each channel. For example, if 5 satellites are captured by the receiver 2a, the reception signal level for 5 satellites is input. The value of PDOP is first referred to for these inputs. The switching control unit 5 has a PD
The threshold value for OP is held, and when it is larger than this threshold value, the PDDP is the same as in the first embodiment.
Is switched to the smaller one.

On the other hand, when PDOP (positioning accuracy reduction rate due to satellite position) is smaller than the threshold value, the received signal level is referred to. The reception invitation level gives the minimum value first in each system (for example, 5 in the RF reception unit 2a).
If satellites have been captured, the received signal level of the satellite with the lowest reception level among the five satellites is calculated). Then, the minimum signal levels of the two systems of the RF receiving section 2a and the RF receiving section 2b are compared, and the switching section 4 is switched to the receiving antenna having the higher received signal level. By controlling in this way, the PDO can be used when the satellite acquisition situation is poor due to shielding.
The GPS positioning can be performed satisfactorily in all reception situations by switching the P operation according to the received signal level when the satellite acquisition situation is good to some extent.

[Fourth Embodiment] FIG. 4 is a block diagram showing an electrical configuration of a diversity receiving GPS receiver according to a fourth embodiment. The two receiving antennas 1a and 1b are installed so as to be uncorrelated with each other. Now, for example, it is assumed that the receiving antenna 1a is selected by the switching unit 4. Then, the reception signal received by the reception antenna 1a is input to the RF reception unit 2. The RF receiving unit 2 demodulates the received signal and sends the received signal level of each satellite received at this time to the switching control unit 5. The demodulated data is sent to the calculation unit 3 and PDOP (positioning accuracy reduction rate due to satellite position) is calculated. At the same time, the current position of the self is calculated and displayed on the display unit 6.

The switching control unit 5 first refers to the value of PDOP. When PDOP is larger than the threshold value held in advance, the switching unit 4 is controlled so that the receiving antenna 1a
The selected state is switched to the selected state of the receiving antenna 1b. When PDOP is smaller than the threshold value, the received signal level is referred to.

When the received signal level is higher than the threshold value held in advance, the current receiving antenna la is held. On the contrary, when the received signal level is lower than the threshold value, the previous switching content is referred to. If the previous switching is by PDOP, the receiving antenna currently in use is held, and if the switching is by lowering the received signal level, the other receiving antenna is switched. Such control is performed, and if the receiving antenna is switched, the switching content is retained. Since it is possible to select the receiving antenna that always obtains good characteristics by repeating such control and perform the positioning calculation, PDOP (the positioning accuracy deterioration rate of the position by the satellite position) is used as the DOP. GDOP (geometric positioning accuracy reduction rate) and TDOP (time-based positioning accuracy reduction rate)
Other DOP values may be used. Further, the receiving system including the RF receiving unit and the calculating unit is described as one system or two systems, but it is needless to say that the present invention may be applied to three or more receiving systems.

Since the second and fourth embodiments have a single receiving system including the RF receiving section 2 and the computing section 3, the configuration is simpler and the cost is lower than that of the other third and fourth embodiments. But it will be advantageous. Further, it is also advantageous in downsizing.

[0044]

EFFECT OF THE INVENTION By using the diversity reception as described above, the satellite is shielded in the city area or the mountainous area, and the GPS is received.
Even in locations where positioning is likely to be difficult, select a receiving antenna with a good reception condition from multiple receiving antennas installed on the moving body or a receiving antenna that can receive satellite groups with less positioning error. Since the reception antenna receives GPS radio waves, it is possible to reduce the time rate of unreceivability and improve the positioning accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of a diversity receiving GPS receiver according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing an electrical configuration of a diversity receiving GPS receiver according to a second embodiment.

FIG. 3 is a block diagram showing an electrical configuration of a diversity receiving GPS receiver according to a third embodiment.

FIG. 4 is a block diagram showing an electrical configuration of a diversity receiving GPS receiver according to a fourth embodiment.

FIG. 5 is a block diagram showing an electrical configuration of a conventional diversity receiving GPS receiver.

[Explanation of symbols]

 la, lb ... Receiving antenna 2, 2a, 2b ... RF receiving section 3, 3a, 3b ... Calculation section 4 ... Switching section 5 ... Switching control section 6 ... Display section

Claims (3)

[Claims] 1. A plurality of receiving antennas for receiving signals transmitted from a plurality of satellites, a switching unit for selectively switching received signals at these receiving antennas, and demodulating the received signals selected by the switching unit. RF
A receiving unit, a calculating unit that calculates the current position of itself based on the multi-tone signal data of the RF receiving unit, and a positioning accuracy deterioration rate (DOP); and a current position that is calculated by the calculating unit. Diversity reception GPS reception comprising: a display unit for displaying; and a switching control unit for controlling the switching unit so that the positioning accuracy deterioration rate for each receiving antenna calculated by the calculation unit becomes smaller. Machine. 2. A plurality of receiving antennas for receiving signals transmitted from a plurality of satellites, a plurality of RF receiving units each connected to each of the receiving antennas for demodulating a received signal, and each of the RF receiving units. A plurality of calculation units that are connected and that calculate the current position of the self based on the demodulated signal data and that calculate the positioning accuracy deterioration rate (DOP); and a switching unit that selectively switches the calculation results of the plurality of calculation units. A display unit that displays the current position based on the calculation result of the calculation unit selected by the switching unit; and a positioning accuracy reduction rate for each reception antenna calculated by each calculation unit that is smaller than the above. A diversity receiving GPS receiver, comprising: a switching control unit that controls the switching unit. 3. The switching control unit switches the switching unit when the positioning accuracy deterioration rate is higher than a predetermined threshold value, and changes the reception signal level from the RF receiving unit when the accuracy deterioration rate is lower than the predetermined threshold value. The diversity receiving GPS receiver according to claim 1 or 2, wherein the switching unit is configured to perform switching with reference to the switching unit.